U.S. Pat. No. 4,019,048, issued May 28, 1991, to the inventor of the present invention, discloses a unit dose syringe which employs a baggie for forming a compartment for containing fluid (medicine) and a needle movable to an exposed position for administering the fluid. The needle, once used, is returned to a protected position, an action which ruptures the baggie and prevents reuse.